Reduction of N2O Emissions from Fluidised Combustion by Reversed Air Staging

Paper in proceeding, 1995

A new method, reversed air staging, for decreasing N2O from fluidised bed combustion, was investigated in a 12 MW circulating fluidised bed boiler. Previous measurements, showing that the N2O is decreased to one fourth (25 ppm), and NO to half(40 ppm) with maintained sulphur capture, were confirmed. Supplementary information on reversed air staging was obtained from additional measurements. By adjusting the temperature and the air ratio it was possible to reduce the CO emission. Thus, the N2O emission can be reduced to the level of 25 ppm, with the emissions of NO, SO2 and CO maintained at about same level as with normal air staging. Low load in combination with reversed air staging resulted in:further reduced emissions. The effect of reversed air staging on the emissions from peat is similar to that of bituminous coal. There is no negative effect of reversed air staging on the combustion efficiency.